Transparencies are transparent or translucent films which may be clear or colored and include textual or graphical data. The data on the transparency may be projected on a distant surface or screen, usually in enlarged form, by an overhead projector so that the data may be observed by a large number of people at once. A typical overhead projector includes a stage upon which the transparency may be placed and light from a source within the projector is directed through the stage and the transparency to a lens system which focusses the light, and an image of the data contained on the transparency, on the distant viewing surface.
The transparency is typically the size of standard letter paper while the stage is of a greater size to accommodate a variety of different possible transparency sizes. Usually this results in light beyond the edges of the transparency being projected to the screen along with the data contained on the transparency. This situation is not a great problem if the transparency is clear, but, if the transparency is colored or translucent, the white light projected from those areas beyond the edges of the transparency is very distracting.
U.S Pat. No. 4,402,585 describes a rectangular envelope which has folding flaps attached to two opposed edges. In use, the transparency is placed within the envelope and the flaps extended to block the light which would otherwise shine past the edges of the transparency. In this fashion, light transmission to the distant viewing surface is limited to that passing through the transparency. These envelopes have proven very successful, but they have the disadvantage that the light must pass through three layers of film, including two comprising the envelope and the transparency itself, which affects the brightness and clarity of the projected image. In addition, the envelope/transparency combination results in a somewhat bulky package.
The transparency itself is most conveniently produced today by the use of a sheet of polymeric film which may have a coating and which can be imaged in a copy machine or laser printer. If a coating is used, it is designed to enhance anchorage of the toner particles used in electrography or xerography to the film. The coating and the film are selected to withstand the temperatures necessary for fusing the toner particles to the transparency sheet.
U.S. Pat. No. 4,480,003 discloses a transparency film for use in plain paper electrostatic copiers. The base of the transparency film is a flexible, transparent, heat resistant polymeric film. An image receiving layer, preferably, a toner-receptive, thermoplastic, transparent polymethyl methacrylate polymer containing dispersed silica particles is coated on a first major surface of the polymeric film. On the second major surface of the film base is coated a layer of non-migratory electrically conductive material, preferably a polymer derived from the reaction of pyrridine and 2 amino-pyrridine with partially chloromethylated polystyrene. It is preferred that a primer coating be interposed between the polymeric film base and the layer of conductive material to provide suitable adhesion of the coating to the film base. It is also preferred that the layer of conductive material be over-coated with a protective coating having additives to control abrasion, resistance, roughness and slip properties. It is disclosed that the sheet can be fed smoothly from a stack and produces clear background areas.
U.S. Pat. No. 4,869,955 discloses an element suitable for preparing transparencies using an electrostatic plain paper copier. The element comprises a polyethylene terephthalate support (polyester), at least one subbing layer coated thereon and, coated to the subbing layer, a toner receptive layer comprising a mixture of an acrylate binder, a polymeric antistatic agent having carboxylic acid groups, a crosslinking agent, butylmethacrylate modified polymethacrylate beads and submicron polyethylene beads. These elements produce excellent transparencies.
U.S. Pat. No. 4,956,225 discloses yet another transparency suitable for electrographic and xerographic imaging comprising a polymeric substrate with a toner receptive coating on one surface thereof. The toner receptive coating comprises blends selected from a group consisting of: poly(ethylene oxide) and carboxymethyl cellulose; poly(ethylene oxide), carboxymethyl cellulose and hydroxypropyl cellulose; poly(ethylene oxide) and vinylidene fluoride/hexafluoropropylene copolymer; poly(chloroprene) and poly(alpha-methylstyrene); poly(caprolactone) and poly(alpha-methylstyrene); poly(vinyl isobutylether) and poly(alpha-methylstyrene); poly(caprolactone) and poly (.alpha.-methylstyrene); chlorinated poly(propylene) and poly(.alpha.-methylstyrene); chlorinated poly(ethylene) and poly(.alpha.-methylstyrene); and chlorinated rubber and poly(.alpha.-methylstyrene). Also disclosed are transparencies with first and second coating layers.
EP Application 0349,227 discloses a transparent laminate film for full color image-forming comprising two transparent resin layers. The first resin layer is heat-resistant, and the second resin layer must be compatible with a binder resin constituting the toner to be used for color image formation. The second resin layer has a larger elasticity than that of the binder resin of the toner at a fixing temperature of the toner. The second resin can be of the same "kind" i.e., type, e.g., styrene-type or polyester type, as the toner binder, as long as the resins differ in storage elasticity.
EP 408197A2 discloses an imageable copy film comprising a thermoplastic polymeric film substrate with a widthwise thermal expansion of 0.01 to 1% at 150.degree. C. and a lengthwise thermal shrinkage in the film of 0.4 to 2.0% at 150.degree. C. The substrate has a receiving layer on at least one surface thereof comprising an acrylic and/or methacrylic resin comprising any film-forming resin, e.g., polymers derived from alkyl esters having up to 10 carbon atoms, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, hexyl, 2-ethylhexyl, heptyl and n-octyl. The use of ethylacrylate or butylacrylate together with an alkylmethacrylate is preferred. Other suitable monomers include acrylonitrile, methacrylonitrile, halo substituted acrylonitrile and (meth)acrylonitrile, acrylamide, methacrylamide, n-methylol acrylamide and methacrylamide, n-ethanol acrylamide and methacrylamide, n-propanol acrylamide and methacrylamide, t-butylacrylamide, hydroxyl ethylacrylamide, glycidyl acrylate, and methacrylate, dimethylamino ethyl methacrylate, itaconic anhydride and half ester of itaconic acid. Vinyl monomers such as vinylacetate, vinylchloroacetate, vinyl benzene, vinyl pyrridine, vinyl chloride, vinylidene chloride, maleic acid, maleic anhydride, styrene and substituted styrene, and the like can optionally be included.
EP 442567A2 discloses a medium for electrophotographic printing or copying comprising a polymeric substrate coated with a polymeric coating having a Tukon hardness of about 0.5 to 5.0 and a glass transition temperature of about 5.degree. to 45.degree. C. The coating comprises at least one pigment which provides a coefficient of static friction of from 0.20 to 0.80 and a coefficient of dynamic friction of from 0.10 to 0.40. The medium has improved image quality and toner adhesion. It is particularly useful in laser electrophotographic printing. The polymer employed in the coating can contain thermosetting or thermoplastic resins, and preferably aqueous acrylic emulsions such as Rhoplex.TM. resins from Rohm and Haas.
U.S. Pat. No. 5,104,731 discloses a dry toner imaging film media having good toner affinity, antistatic properties, embossing resistance and good feedability through electrophotographic copies and printers. The media comprises a suitable polymeric substrate with an antistatic matrix layer coated thereon. The matrix layer has resistance to blocking at 78.degree. C. after 30 minutes and a surface resistivity of from about 1.times.10.sup.8 to about 1.times.10.sup.14 ohms per square at 20.degree. C. and 50% relative humidity. The matrix contains one or more thermoplastic polymers having a T.sub.g of 5.degree. C. to 75.degree. C., and at least one crosslinked polymer which is resistant to hot roll fuser embossing, at least one of the polymers being electrically conductive.
U.S. patent application Ser. No. 947,252 to Ali et. al., filed Sep. 18, 1992 and assigned to the assignee of the present invention, discloses another film and coating which is useful in making transparencies in a standard copy machine or laser printer. The subject matter of this patent application is described in greater detail below. This patent application, U.S. Pat. No. 4,402,585 and the patents and patent applications described above relating to the production of transparency in a copy machine or laser printer are hereby incorporated by reference.